Ernest Casimir

Ernest or Ernst Casimir may refer to:


 * Ernest Casimir, Count of Nassau-Weilburg (1607–1655), founder of the younger line of Nassau-Weilburg
 * Ernest Casimir I, Count of Nassau-Dietz (1573–1632)
 * Prince Ernest Casimir of the Netherlands (May 1822 – August or October 1822)
 * Ernst Casimir I, 1st Prince of Ysenburg and Büdingen (1781–1852)
 * Ernst Casimir II, Prince of Ysenburg and Büdingen (1806–1861)